Power divider for antenna array using digital ferrite phase shifters



.1. o. WOERMBKE ETAL 3,474,454 rowan nxvmma ron ANTENNA ARRAY usmc DIGITAL FERRITE PHASE SHIFTERS Filed March 10, 1967 2 Sheets-Sheet 1 FIG.3

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PHASE SHIFTERS 28 FEED SYSTEM I Oct. 21, 1969 J. D. WOERMBKE ET AL 3,474,454 POWER DIVIDER FOR ANTENNA ARRAY USING DIGITAL FERRITE PHASE SHIFTERS Filed larch 10 1967 v 2 Sheets-Sheet 2 INSULATING FILM\ I United States Patent U.S. Cl. 343778 6 Claims ABSTRACT OF THE DISCLOSURE A stacked microwave antenna array is fed by a plurality of dual power dividers. The ratio frequency source is divided down by successive steps from a single waveguide by means of dual power dividers to the final power dividers mounted side by side, feeding the inividual elements of the array. In each of the final power dividers there is incorporated a multi-bit ferrite phase shifter, each comprising a plurality of ferrite cores selectively energized individually to produce digital phase shift in the microwave energy supplied to each element of the antenna matrix. A wiring arrangement for carrying the magnetizing current into the ferrite segments of the closely stacked power dividers is described.

In copending application Ser. No. 396,121, filed Sept. 14, 1964, in the name of William J. Parr-is for Non-Reciprocal Microwave Apparatus, there is described and claimed a device for effecting non-reciprocal phase shift or attenuation of microwave energy in microwave guides. That application is owned by the assignee of this application. These phase shift mechanism of that application and the present invention is a multi-bit unit comprising a plurality of square loop gyromagnetic ferrite rectangular toroid elements, or cores, disposed symmetrically along the axis of a microwave guide. The ferrite cores have a central aperture in which is disposed a longitudinal conductor energized from a DC power source to establish closed path magnetization in the square loop ferrite material in planes transverse to the direction of propogation for producing a selected digital phase shift in the microwave energy propagated in the waveguide. The amount of digital phase shift produced by each core is dependent upon the length of the ferrite core and, accordingly, ferrite cores of different lengths are provided to produce different quantized amounts of phase shift, such as 22 /2", 45", 90 and 180.

This invention relates to microwave power dividers and more particularly to multi-bit latchable ferrite digital phase shifters incorporaed into a power divider. More particularly, this invention relates to such phase shifters incorporated into microwave power dividers feeding the individual elements of a closely stacked antenna array and to the wiring arrangement for supplying the magnetization currents to the toroidal ferrite core.

The invention is illustrated in connection with a stacked radar antenna array wherein the beam scanning is accomplished by digitally varying the relative electrical phase of the electromagnetic wave energy radiated from the radiating elements of the array. As the description proceeds, it will be apparent, however, that the basic concept of the invention is not limited to the application ice shown and described herein. The invention resides in the arrangement of the conductors for magnetizing the multi bit ferrite phase shifters, the arrangement being particularly adapted to an environment, such as that illustrated, in which the phase shifters are mounted in power dividers stacked in a tight three-dimensional array.

Broadly speaking, the present invention provides a feasible, simple and efficient system for controlling the lobe switching of a very high gain antenna matrix having very closely spaced radiation elements. It is accomplished by incorporating a multi-bit ferrite phase shifter in a dual power divider feeding microwave horn antenna elements in a stacked array.

The multiple bit ferrite phase shifter makes it possible to produce the phase shifting and thus provide lobe switching but each ferrite core requires an energizing wire extending from the end of each element so that when the microwave radiating elements are stacked tight- 1y together they present a problem in positioning the conductors for providing the closed loop magnetization bias in the ferrite cores.

In order to facilitate an understanding of the invention the two major components; namely, the ferrite phase shifter and the dual power divider will be mentioned here briefly for background purposes.

In the aforementioned copending patent application this is disclosed and claimed a non-reciprocal phase shifter which is basically that illustrated in FIG. 5. It comprises a section of microwave guide of rectangular cross section, of such dimensions as to support the propagation of microwave energy of a selected operating frequency in the dominant TE mode, so that the electric field is perpendicular to the direction of propagation and to the plane of the paper. In the waveguide there is centrally disposed in axial alignment gyromagnetic ferrite cores of various lengths.

The ferrite cores have a square loop magnetization characteristic curve and when they are energized to saturated condition they produce a shift in the phase of the microwave energy being propagated through the waveguide. The amount of phase shift of each core is a function of its length so that by properly selecting the length of the individual cores a multi-bit phase shifter is provided. Then, by producing square loop magnetization bias to saturation, selectively, in the cores digitized control of the phase shift to the microwave energy can be provided.

The present invention provides an arrangement for placing the conductors in the wave guide through which current is selectively supplied to magnetize, the ferrite cores without interfering with the normal operation of the waveguide.

The primary object of this invention is to provide novel and improved means for energizing the ferrite cores in microwave phase shifters, in general, and power dividers in particular where the waveguide sections are in contiguous side-by-side relation.

Another object is to provide a novel and improved means for placing the wires for energizing the ferrite cores of a multi-bit phase shifter in such a manner as to enable the coordination of the phase shift in all of the radiating elements of an antenna array simultaneously to produce lobe switching action.

Other and further objects will become apparent from the following description when considered in connection with the accompanying drawings, in which:

FIGURE 1 is an isometric view of an antenna matrix incorporating the present invention;

FIG. 2 is a schematic circuit diagram of the feed system for the antenna matrix of FIG. 1;

FIG. 3 is a plan view of one deck of the antenna array of FIG. 1 and including the feed system;

FIG. 4 is a side elevational view of the antenna matrix of FIG. 1, including the feed system;

FIG. 5 is a longitudinal sectional plan view illustrating the digital phase shifter;

FIG. 6 is a longitudinal sectional plan view of the power divider incorporating the dual phase shifter;

FIG. 7 is an enlarged longitudinal elevational view of the side of the encapsulating insulating strip facing the center of the waveguide and carrying the conductors for magnetizing the ferrite cores of the phase shifter;

FIG, 8 is an enlarged side elevational view of the opposite side of the insulating strip; and

FIG. 9 is an end elevational view of the insultaing strip and conductors of FIGS. 7 and 8.

Turning now to a more detailed description of the digital phase shifter associated with the present invention, as indicated in FIG. 5, each of the ferrite cores 10, 11 and 12 has an aperture running lengthwise of the core through which suitable conductors 14, 16 and 17, respectively, are disposed. In order to provide the desired digital control of the phase shifter the conductors extending through the respective cores must be selectively energized to produce closed loop path magnetization about the apertures of the cores. It will be readily apparent that the conductors 14, 16 and 17 may be separate entities or they may be portions of a continuous conductor extending through the separate cores, Then the portions 14, 16 and 17 can be selectively energized, jointly or severally, through transversely extending leads 18, 19, 20 and 21 which may be connected to external energizing circuitry. Upon application of a spike pulse of current through the conductors in the apertures of the cores, the ferrite material is magnetized in one stable latched state, thus introducing an electrical phase shift, with respect to the incident microwave energy in the waveguide. If the polarity of the current spike is reversed, the ferrite will again become latched, but in the opposite sense. The second state produces a new and different phase shift 0f the microwave. Thus, simply by proper pulsing to latch the ferrite core, or cores, in the waveguide a differential phase shift A= is produced. As previously mentioned, the amount of phase shift depends upon the length of the individual core that is magnetized. Therefore, a multi-bit phase shifter can be made where the core 10 may produce 180 phase shift, the core 11 may produce a phase shift of 90, and the core 12 may produce a phase shift of 45, under saturation magnetization. The lengths of the cores may be varied as desired, to produce other steps of phase shift.

The present invention stemmed from a requirement that this type of phase shifter be utilized in an antenna matrix such as that illustrated in the previous figures of the drawings in which the radiating elements are microwave horns stacked very tightly in side-by-side relation in a type of matrix as illustrated in FIG. 1.

From the description of the multi-bit ferrite phase shifter, it is readily apparent that a very large number of wires must enter into the waveguide through one side wall thereof and be connected to the central magnetizing conductors in a multi-bit device in order to selectively magnetize the ferrite cores for digital phase shift control. Also these wires energized or unenergized must not interfere with the microwave propagation in the waveguide.

The number of such wires will be 2 N for each phase shifter where N is the number of ferrite cores in each phase shifter asembly, Accordingly, with at least three separate core elements in each phase shift assembly, as illustrated, six wires must be brought out through the side wall of the phase shifting section of the microwave guide. This accounts for the large number of conductors shown in FIG. 1 which must be connected to a suitable energizing source, such as a computer controlled matrix, for lobe switching the gain pattern of the antenna. Ordinarily, when the phase shifter of the type illustrated in FIG. 5 is used by itself, there are two side walls through which the energizing wires can be brought out from the inside of the guide but this cannot be done in the antenna array illustrated.

Referring to the arrangment schematically illustrated in FIG. 2, for feeding the microwave energy to the type of matrix shown in FIG. 1, it will be seen that the radio frequency power is divided down from a single microwave guide 25 fed by a microwave generator (not shown) through waveguides 26, 27 and 28, which is referred to as the feed system, to further power dividers 29, which feed power dividers and dual phase shifters 31 wherein the microwave power is finally divided and supplied to the microwave horns H through the dual phase shifters of the present invention.

From the above it is seen that the antenna matrix of FIG. 1 requires that all of the dual phase shifters 31 be mounted closely together side-by-side. Since only a common septum separates the dual phase shifters one side wall of each of the pair of waveguide sections of each phase shifter is eliminated, as shown in FIG. 6, and this restricts the space available for the wires for magnetizing the ferrite cores. Furthermore, the three-dimensional packaging of the microwavehorn radiating array renders virtually impossible access to either the top or the bottom walls of the phase shifters. This presents the problem solved by the present invention, namely, means for bringing the magnetizing wires out of the waveguides without interfering with the operation of the phase shifter.

Although it is well known in the art that with a core of ferrite material in the center of a waveguide operating in the TE mode most of the electric field will be concentrated in the ferrite material, it was found that with the arrangement of the present invention the electric field was so highly concenctrated in the center part of the guide that the conductors could be brought out transversely from the center of the cores to conductors positioned close to and parallel with the side walls of the phase shifter waveguide sections as described herein without susbtantially interfering with the operation of the phase shifter.

The three dimensional antenna array illustrated also presented the problem of bringing out the energizing wires from the phase shifter waveguide section without interfering with the operation of the feed system. This mechanical design problem was solved by incorporating a multi-bit ferrite phase shifter of the type shown in FIG. 5 into each side of the novel 3 db power divider shown in FIG. 6 and then encapsulating the conductors in a plastic form or strip 51 bonded to the inner sides of the outer walls of the power dividers. The arrangement for supporting the strips 51 on the outer side walls of the power divider-dual ferrite phase shifter section is shown in FIG. 6.

Referring now to FIG. 6, the 3 db power divider, in accordance with the present invention, has a phase shifter of the type shown in FIG. 5 incorporated in each side thereof. Each of these power dividers with the dual phase shifters serves as the final coupling between the microwave source and a pair of the radiating horns of the antenna matrix and are properly operated to electronically steer the gain pattern of the antenna matrix. Each of the power dividers and dual phase shifter units 31 is fed by one of the waveguides 29 in the feed system of FIG. 2. These power dividers comprise a microwave guide stub section 29a which is, effectively, an extension of the waveguide 29. The latter is of rectangular cross section and is of such size as to support the dominant TE mode of the desired frequency. The power divider units 31 are approximately twice as wide as waveguide section 29a but have the same vertical dimension since it is to handle microwaves of the same frequency as that propagated in waveguide 29. A central septum 33 longitudinally divides power divider unit 31 electrically into two separate microwave sections 31a, 31b so that it is substantially the same as two sections of waveguide sections arranged side-byside. When microwave energy is propagated from waveguide 29 down the unit 31 toward the right microwave energy will couple into the side-by-side sections of the power divider 31 and will be equally distributed between the two sections.

In order to provide the lobe switching of the gain pattern of the antenna array the phase of the microwave energy in the two sections 31a and 31b is varied in accordance with functional programs well understood in the art. A means for accomplishing this relative phase adjustment includes the ferrite cores 32, 33 and 34 coaxially aligned in section 31a of the power divider on one sde of the septum 33 and the ferrite cores 36, 37 and 38 coaxially aligned on the opposite side of the septum 38. The oppositely paired elements are identical. The axial length of cores 32 and 36 are such that when they have their magnetization reversed from one circumferential direction to the other, they will provide a differential phase shift of 45. Similarly, the axial length of the cores 33 and 37 are such that when they go through similar magnetization reversal they will provide a differential phase shift of 90, while the elements 34 and 38 are of such axial length as to provide a phase shift of 180.

The means for magnetizing the ferrite cores of each section of the phase shifter may be in the form of a single longitudinal conductor extending through the central apertures of the aligned ferrite cores of each section, of the phase shifter, with transversely extending conductors, or may be a part of a loop for each core which includes a longitudinally disposed portion and two transverse extending conductors at the opposite ends of each core connected to the conductors embedded in the plastic strip preferably adhesively secured to the outer walls of the sections 31a and 31b. The latter arrangement is illustrated in FIG. 6 wherein each of the ferrite cores 32, 33, 34, 36, 37 and 38 have U-shaped loops 42, 43, 44, 46, 47 and 48, respectively, associated therewith, each of which has a portion 42a, 43a, 44a, 46a, 47a and 48a extending longitudinally in the aperture of the respective ferrite core and transversely extending portions (4212-0, 43b-c, 44b-c, 46bc, 47bc, and 48bc) each connected, respectively to the conductors extending along the outer side walls of the power dividers and leading to the external energizing circuits. The arrangement in the two side-by-side sections of the power divider i identical.

The conductors for connection to the external circuit for energizing the magnetizing conductors are carried by encapsulating plastic insulating strips and enlarged illustrations of these are shown in FIGS. 8 and 7 at 51. The side of the strip which faces the center line of the phase shifter section is illustrated in FIG. 7 while the opposite side is shown in FIG. 8. The loop 42 has its transverse portions. connected respectively, to the flat longitudinal conductors 52 and 53 carried by the insulating strip 51 and these conductors are on the side of the strip which is adhered to the inside of each of the outside walls of the power divider unit. The loop 43 has its left-hand end con nected to the flat conductor strip 54 while the right-hand end of the loop is connected to the flat conductor 56. The left-hand end of the loop 44 is connected to the flat strip 57 while the right-hand end of the loop is connected to the flat strip 58. Each of the several loops may be connected to a suitable source of signal pulse energy, symbolically represented herein by the batteries 66 and 67.

Since the gyromagnetic ferrite cores are operated in the two opposite saturated magnetic states, the signal pulses can take any form which is capable of providing a short current pulse of sufiicient magnitude and selected polarity to latch the respective elements into the desired saturated state. The batteries, with the appropriate switch means, may be utilized for independently and selectively energrzmg the magnetizing loops in a manner which could be produced at high speed by a computer mechanism to provide the program for the desired lobe switching. Such a computer would be the electrical equivalent of batteries 66 and 67 connected in the circuit configuration with the double pole, double throw switches 68 and 69. The battery 66 supplies the circuit through the switch 68 which lncludes the loop 42, the longitudinal portion of which extends through the central aperture of ferrite element 32. Lilrewise, the battery 67 is in a circuit which includes the sw tch 69 and the loop 43, the longitudinal portion of Wl'llCh extends through the central aperture in the ferrite element 31. It is also apparent that the battery 67 can be connected in a circuit which includes the switch 69 and the loop 44, the central portion of which extends through the central aperture of the ferrite element 34.

It is to be understood, of course, that the illustration of the batteries and switches is merely for the purpose of showing some mean for producing the closed-loop path latching magnetization in the ferrite cores and that in actual practice a computer matrix would be utilized for supplying pulsed energization for switching all of the cores of the power dividers of the antenna matrix with the proper permutations and combinations and sequence to attain the desired steps of phase shift in order to provide the lobe switching function of the antenna. Only three ferrite cores in each phase shifter are shown, but it is obvious that any greater or lesser number could be used and their lengths could be chosen in order to vary the steps of phase shift as desired.

In order to prevent the transverse portions of the magnetizing loops from inducing closed-path magnetic flux in the ferrite elements in planes parallel to the axes of the waveguide sections suitable non-magnetic dielectric spacers 72, 73, 74, 76, 77, 78, 79 and 81 are provided for the purpose of spacing the ferrite cores. The transverse conductors are connected to the central conductor in the center of the dielectric block.

We claim as our invention:

1. In an electronically controlled scanning antenna array having a plurality of radiating elements placed sideby-side in juxtaposed relation, a plurality of power divider means each including a main waveguide and a pair of waveguide sections for feeding said elements in pairs, each of said pairs of waveguide sections having electromagnetic wave phase shifting means comprising a plural- 1ty of gyromagnetic ferrite toroidal cores disposed in axial alignment with each other and extending axially inside each respective waveguide sections, current carrying conductor means for producing closed-loop path magnetization in said cores in planes transverse to the axes of said waveguide sections, said conductor means having a portion extending axially through said toroidal cores, laterally extending portions at the opposite ends of said cores and additional portions extending from one end of the respective waveguide sections adjacent and parallel to the inner side of the outer walls of the respective waveguide sections.

2. The combination as set forth in claim 1, in which the portions of said conductor means adjacent said walls arel embedded in plastic insulating strips secured to said wa ls.

3. The combination as set forth in claim 1 in which said radiating elements are rectangular horns each constituting an extension of the respective pairs of waveguide sections of said power divider means.

4. The combination as set forth in claim 3, in which said radiating elements are waveguide horns and said waveguide sections are open-ended.

5. The combination as set forth in claim 1, in which said pairs of waveguide sections are open-ended and have a common sidewall.

7 6. The combination as set forth in claim 1, in which said cores are of different length to thereby provide digital phase shift of diiferent selected amount when said cores are selectively latched in their magnetization states, and means for selectively magnetizing said cores through said conductor means.

References Cited UNITED STATES PATENTS 3,041,605 6/1962 Goodwin et a1 33324.l

8 OTHER REFERENCES The Microwave Journal, Tech. Briefs No. 652, p. 43, April 1965.

5 HERMAN KARL SAALBACH, Primary Examiner F. P. BUTLER, Assistant Examiner US. Cl. X.R. 

